Making a HTTPS call to download a file

I have this current situation where i have to log on to a website and download a text file. i want to automate this process by using webMethods to make the call to the website and download the file. But when i am trying the service “PUB.CLIENT:HTTP”, it returns me the HTML of the login page of that website.
Is there a way in which i can get the session object from the first call and use that in the next “PUB.CLIENT:HTTP” call to download the file.
Note: I have the direct URL to the file to be downloaded, but when i try it manually it first redirects to the login page and then after authentication it directly gives me the dialog box to open/save the file.
Please advice on what can be done.
Thanks in advance

Try exploring loadDocument service.